Independently and not as an agent of the Government, the Conractor shall exert its best efforts to study: The role of macrophages as principal effector cells, or amplifying effector cells, in the expression of anti-tumor immunity; Cellular interacitons, with special reference to the role of soluble mediators, in the production of macrophage cytotoxicity and the inhibition of immunity; and The mode of action of substances which non-specifically increase resistance to tumors and also increase macrophage activity in the induction of tumor immunity.